California Regional Water Quality Control Board, Los Angeles Region

Calleguas Creek Delistings

Draft 12/03/01

Calleguas Creek Reach 9A, Camrosa Diversion

Dissolved Oxygen (Delisting)

Summary of Proposed Action

Calleguas Creek Reach 9A, or Camrosa Diversion, extends from the confluence with Calleguas Creek Reach 2 to the start of Calleguas Creek Reach 9B, Conejo Creek, at the Camrosa Diversion. Calleguas Creek Reach 9A is proposed to be removed from the 2002 305(b) water quality assessment as it is fully supporting (not impaired) as it meets the Basin Plan objective for dissolved oxygen. The beneficial use affected by this action is aquatic life.

Table 1. 303(d) Listing/TMDL Information

Waterbody Name

/ Calleguas Creek Reach 9A -
Camrosa Diversion / Pollutants/Stressors / Dissolved Oxygen
Hydrologic Unit / 403.12 / Source(s) / NA
Total Waterbody Size / 100.1 Miles + Estuary / TMDL Priority / TMDL Analytical Unit 1
Size Affected / 1.7 Miles / TMDL Start Date (Mo/Yr) / NA
Extent of Impairment / Entire reach / TMDL End Date (Mo/Yr) / NA

Watershed Characteristics

Calleguas Creek and its major tributaries, Revolon Slough, Conejo Creek, Arroyo Conejo, Arroyo Santa Rosa, and Arroyo Simi drain an area of 343 square miles in southern Ventura County and a small portion of western Los Angeles County. This watershed, which is elongated along an east-west axis, is about 30 miles long and 14 miles wide. The northern boundary of the watershed is formed by the Santa Susana Mountains, South Mountain, and Oak Ridge; the southern boundary is formed by the Simi Hills and Santa Monica Mountains.

Water Quality Objectives Now Attained.

The Basin Plan limits for dissolved oxygen read as follows: "At a minimum (see specifics below), the mean annual dissolved oxygen concentration of all waters shall be greater than 7 mg/L, and no single determination shall be less than 5.0 mg/L, except when natural conditions cause lesser concentrations.

"The dissolved oxygen content of all surface waters designated as WARM shall not be depressed below 5 mg/L as a result of waste discharges."

Reach 9 is designated as having intermittent warm freshwater habitat.

Beneficial Uses Affected

§ Warm freshwater habitat

Data Assessment

Table 2. Summary of Dissolved Oxygen for Calleguas Creek Reach 9A - Conejo Creek Camrosa Diversion.

Dates of Sampling / 7/97-8/00
Number of Samples (n) / 111
Minimum Data Value / 3.4 mg/L
Maximum Data Value / 10.2 mg/L
Median Data Value / 7.3 mg/L
Arithmetic Mean Value / 7.3 mg/L
Standard Deviation / 1.51 mg/L
Number (Percent) above Objective / 6 samples or 5.5% have levels less than 5 mg/L.

Potential Sources

References

Calleguas Creek Chloride TMDL 2001

Camarillo WWTP NPDES Reports

Basin Plan 1994

Watershed Management Initiative Chapter 2000

California Regional Water Quality Control Board, Los Angeles Region

Calleguas Creek Reach 10, Conejo Creek, Hill Canyon

Dissolved Oxygen (Delisting)

Summary of Proposed Action

The Hill Canyon reach of Conejo Creek, also called Calleguas Creek Reach 10, extends from the confluence with Arroyo Santa Rosa to the confluence with the North Fork of Conejo Creek, and includes the North Fork to just above the Hill Canyon Wastewater Treatment Facility (WWTF). This reach is proposed to is proposed to be removed from the 2002 305(b) water quality assessment as it is fully supporting (not impaired) as it meets the Basin Plan objective for dissolved oxygen. The beneficial use affected by this impairment is warm water habitat (WARM).

Table 1. 303(d) Listing/TMDL Information

Waterbody Name

/ Calleguas Creek Reach 10 / Pollutants/Stressors / Dissolved Oxygen
Hydrologic Unit / 403.64 / Source(s) / NA
Total Waterbody Size / 100.1 Miles + Estuary / TMDL Priority / TMDL Analytical Unit 1
Size Affected / 3.4 Miles / TMDL Start Date (Mo/Yr) / NA
Extent of Impairment / Entire Reach / TMDL End Date (Mo/Yr) / NA

Watershed Characteristics

Land uses vary throughout the watershed. Urban developments are generally restricted to the city limits of Simi Valley, Moorpark, Thousand Oaks, and Camarillo. Although some residential development has occurred along the slopes of the watershed, most upland areas are still open space, however, golf courses are becoming increasingly popular to locate in these open areas. Agricultural activities, primarily cultivation of orchards and row crops, are spread out along valleys and on the Oxnard Plain.

Water sources for Reach 10 include water from upstream Arroyo Conejo North and South Forks, Reaches 12 and 13, urban and agricultural runoff, and effluent from Hill Canyon WWTF.

Water Quality Objectives Now Attained

"The dissolved oxygen content of all surface waters designated as WARM shall not be depressed below 5 mg/L as a result of waste discharges."

Reach 10 is designated as having existing warm freshwater habitat.

Beneficial Uses Affected

§ Warm freshwater habitat.

Data Assessment

Table 2. Summary of Dissolved Oxygen Data for Calleguas Creek Reach 10.

Dates of Sampling / 7/97-12/00
Number of Samples (n) / 81
Minimum Data Value / 3.4 mg/L
Maximum Data Value / 11.5 mg/L
Median Data Value / 7.3 mg/L
Arithmetic Mean Value / 7.33 mg/L
Standard Deviation / 1.35 mg/L
Number (Percent) above Objective / 3 samples or 4% were below the criteria of 5 mg/L.

Potential Sources

References

Calleguas Creek Chloride TMDL 2001

Basin Plan 1994

Watershed Management Initiative Chapter 2000

Calleguas Creek Ambient Water Quality Monitoring

Hill Canyon WWRP NPDES Report

California Regional Water Quality Control Board, Los Angeles Region

Calleguas Creek Reach 11, Arroyo Santa Rosa

Dissolved Oxygen (Delisting)

Summary of Proposed Action

Calleguas Creek Reach 11, or Arroyo Santa Rosa, extends from the headwaters to Reach 10, Conejo Creek Hill Canyon, where it connects only during periods of high flow. Calleguas Creek Reach 11 is proposed to be removed from the 2002 305(b) water quality assessment as it is fully supporting (not impaired) as it meets the Basin Plan objective for dissolved oxygen. The beneficial use affected by this impairment is warm water habitat (WARM).

Table 1. 303 (d) Listing/TMDL Information

Waterbody Name

/ Calleguas Creek Reach 11 -
Arroyo Santa Rosa / Pollutants/Stressors / Dissolved Oxygen
Hydrologic Unit / 403.63
403.64
403.65
403.67 / Source(s) / NA
Total Waterbody Size / 100.1 Miles + Estuary / TMDL Priority / TMDL Analytical Unit 1
Size Affected / 10.2 Miles / TMDL Start Date (Mo/Yr) / NA
Extent of Impairment / Entire reach / TMDL End Date (Mo/Yr) / NA

Watershed Characteristics

Calleguas Creek Reach 11, or Arroyo Santa Rosa, extends from the headwaters to Reach 10, Conejo Creek Hill Canyon, where it connects only during periods of high flow. The confluence with Reach 10 is usually dry. Olsen Road WRP currently discharges to this reach, but it is scheduled to be decommissioned, with its influent diverted to Hill Canyon WWTF.

Water Quality Objectives Now Attained.

"The dissolved oxygen content of all surface waters designated as WARM shall not be depressed below 5 mg/L as a result of waste discharges."

Reach 11 is designated as having intermittent warm freshwater habitat.

Beneficial Uses Affected

§ Warm freshwater habitat

Data Assessment

Table 2. Summary of Dissolved Oxygen Data for Calleguas Creek Reach 11, Arroyo Santa Rosa.

Dates of Sampling / 7/97-8/00
Number of Samples (n) / 41
Minimum Data Value / 7.2 mg/L
Maximum Data Value / 11.3 mg/L
Median Data Value / 9.7 mg/L
Arithmetic Mean Value / 9.46 mg/L
Standard Deviation / 0.84 mg/L
Number (Percent) above Objective / None, 0%.

Potential Sources

NA.

References

Calleguas Creek Chloride TMDL 2001

Calleguas Creek Characterization Study 2000

Watershed Management Initiative Chapter 2000

Basin Plan (1994)

California Regional Water Quality Control Board, Los Angeles Region

Calleguas Creek South – Reach 2

Water Column Toxicity

Summary of Proposed Action

Delisting is proposed for Reach 2, Calleguas Creek South, for water column toxicity, which affects aquatic life beneficial uses.

Table 1. 303(d) Listing/TMDL Information

Waterbody Name

/ Calleguas Creek R2 / Pollutants/Stressors / Water Column Toxicity
Hydrologic Unit / 403.12 / Source(s) / N/A; delisting
Total Waterbody Size / TMDL Priority / N/A; delisting
Size Affected / 4.4 / TMDL Start Date (Mo/Yr) / N/A; delisting
Extent of Impairment / Entire reach / TMDL End Date (Mo/Yr) / N/A; delisting

Watershed Characteristics

Calleguas Creek and its major tributaries, Revolon Slough, Conejo Creek, Arroyo Conejo, Arroyo Santa Rosa, and Arroyo Simi drain an area of 343 square miles in southern Ventura County and a small portion of western Los Angeles County. This watershed, which is elongated along an east-west axis, is about 30 miles long and 14 miles wide. The Santa Susana Mountains, South Mountain, and Oak Ridge form the northern boundary of the watershed; the Simi Hills and Santa Monica Mountains form the southern boundary.

Land uses vary throughout the watershed. Urban developments are generally restricted to the city limits of Simi Valley, Moorpark, Thousand Oaks, and Camarillo. Although some residential development has occurred along the slopes of the watershed, most upland areas are still open space; however, golf courses are becoming increasingly popular to locate in these open areas. Agricultural activities, primarily cultivation of orchards and row crops, are spread out along valleys and on the Oxnard Plain.

Mugu Lagoon, located at the mouth of the watershed, is one of the few remaining significant saltwater wetland habitats in southern California. The Point Mugu Naval Air Base is located in the immediate area and the surrounding Oxnard Plain supports a large variety of agricultural crops. These fields drain into ditches that either enter the lagoon directly or through Calleguas Creek and its tributaries. Other fields drain into tile drain systems that discharge to drains or creeks. Also in the area of the base are freshwater wetlands created on a seasonal basis to support duck hunting clubs. The lagoon borders on an Area of Special Biological Significance (ASBS) and supports a great diversity of wildlife including several endangered birds and one endangered plant species. Except for the military base, the lagoon area is relatively undeveloped.

Supplies of ground water are critical to agricultural operations and industry (sand and gravel mining) in this watershed.

Pollutants from nonpoint sources have impacted aquatic life in both Mugu Lagoon and the inland streams of this watershed. DDT, PCBs, other pesticides, and some metals have been detected in both sediment and biota collected from surface waterbodies of this watershed. Additionally, ambient toxicity has been revealed in several studies from periodic toxicity testing in the watershed (ammonia from POTWs and pesticides such as diazinon and chlorpyrifos are implicated). Fish collected from Calleguas Creek and Revolon Slough exhibit skin lesions and have been found to have other histopathologic abnormalities. High levels of minerals and nitrates are common in the water column as well as in the groundwater. Sediment toxicity is also elevated in some parts of the lagoon. Reproduction is impaired in the resident endangered species, the light-footed clapper rail due to elevated levels of DDT and PCBs. Overall, this is a very impaired watershed. It appears that the sources of many of these pollutants are agricultural activities (mostly through continued disturbance and erosion of historically contaminated soils), which cover approximately 25% of the watershed along the inland valleys and coastal plain, although the nearby naval facility has also been a contributor. Other nonpoint sources include residential and urban activities, which are present over approximately 25% of the watershed. The remaining 50% of the watershed is still open space although there is a severe lack of benthic and riparian habitat.

Mugu Lagoon as well as the Calleguas Creek Estuary are considered candidate toxic hot spots under the Bay Protection and Toxic Cleanup Program (BPTCP) for reproductive impairment (the endangered clapper rail), exceedance of the state Office of Environmental and Health Hazard Assessment (OEHHA) advisory level for mercury in fish, and exceedance of other tissue guidelines for DDT in fish and sediment concentrations of DDT, PCB, chlordane, chlorpyrifos, sediment toxicity and degraded benthic infaunal community.

Primary issues related to POTW discharges include ammonia toxicity and high mineral content (i.e., salinity), the latter, in part, due to imported water supplies.

Water Quality Objectives Attained

New delisting resulting from testing one site downstream of Camrosa Wastewater Treatment Plant for chronic water column toxicity using the fathead minnow and Ceriodaphnia (see data assessment table for test results).